The Living World - Environmental Science - page 42

Ecosystem Diversity
Biodiversity
The total of all species in a given area at a specific time encompasses biological diversity, or biodiversity. Bi-
odiversity can be viewed in terms of ecosystems, species, or genetics.
• Ecosystem diversity is the variety of ecosystems within a specific area, including communities and hab-
itats. An ecosystem includes all living organisms in an area. A large section of prairie land will have
lower biodiversity than a forested area with many different varieties of trees supporting many types of
species.
• Species diversity is the number (or variety) of a species within a particular community. A species is clas-
sified as a group of organisms that share particular sets of characteristics and can breed and reproduce to
create fertile offspring. The higher number of different species in an area means there is high biod-
iversity. In evaluating species diversity, there are two key components: species richness and relative
abundance. Species richness is the number of species in an area, while relative abundance is the num-
ber of each species in relation to one another, or how equal the numbers are of each species.
• Genetic diversity is the variation of heritable DNA among individuals of a species or population. All or-
ganisms have different DNA makeup, so a population of organisms with a large number of individuals
will have more genetic diversity than a population with a few individuals. Populations with low genetic
diversity are at higher risk for extinction because fewer genetic variations are available to allow for ad-
aptation to environmental change. As an example, if the climate in a region is altered dramatically and
becomes warmer, the organisms with thicker fur may not survive, thus leaving those with thinner coats
to survive and reproduce. Also, if only a few individuals have this variation, the whole population could
suffer. In addition, low genetic diversity can lead to inbreeding issues when organisms with a very simil-
ar genetic makeup breed and produce offspring with physical problems.
Biodiversity is not evenly distributed because factors such as climate, altitude, and topography affect what spe-
cies live in particular locations. Species richness is greater closer to the equator. This difference in richness
from poles to equator is called the latitudinal gradient and is supported by the consistent amount of solar radi-
ation, humidity, and precipitation near the equator. The result is increased plant life near the equator, which, in
turn, supports numerous animal populations.